Hot topping an ingot mould by adhesively bonding slabs to the mould wall

ABSTRACT

INGOT MOULD HOT TOP SLABS ARE ADHERED IN PLACE VIA A SOFT, DIFFICULTLY FLAMMABLE, DEFORMABLE LAYER BETWEEN THE SLABS AND THE MOULD WALL, WHICH ACTS TO MATCH THE CONTOURS TOGETHER AND TO TAKE UP IRREGULARITIES. THE SOFT LAYER IS ADHERED TO THE MOULD WALL VIA A LAYER OF ADHESIVE.

July 31, 1973 1 NANCARROW ET AL HOT TOPPlNG AN lNGU'l MOULD BYADHESIVELY BONDING SLABS TO THE MOULD WALL Filed Sept. 3, 1970 UnitedStates Patent Olfice 3,749,628 Patented July 31, 1973 U.S. Cl. 156-30915 Claims ABSTRACT OF THE DISCLOSURE Ingot mould hot top slabs areadhered in place via a soft, diflicultly flammable, deformable layerbetween the slabs and the mould wall, which acts to match the contourstogether and to take up irregularities. The soft layer is adhered to themould wall via a layer of adhesive.

This invention relates to the provision of hot topping linings in ingotmoulds. For simplicity of expression the term ingot moulds is usedthroughout, but it IS to be understood that this term, both in thefollowing descr1ption and in the claims, includes head boxes for suchmoulds, as the invention is equally applicable to the provision of hottopping linings in head boxes.

Many methods are known for fixing hot toppmg slabs or other elements inthe head portion of ingot moulds. Methods involving the use of extraapparatus, e.g. clips, nails, rods, ties, are generally cumbersome andno particular such method has gained any widespread acceptance.

Various adhesive systems for attaching lining slabs to mould walls havebeen proposed, but none has given consistently satisfactory results,principally due to the inability of the adhesive satisfactorily toperform its function under the conditions normally experienced insteelworks practice.

The walls of ingot moulds are often uneven and contain cracks, pits, andcrazing, so that when a slab of lining material, which is usually fiatcompared to the ingot mould wall, is pressed against the wall, contactis only established at a few places. Thus the face of the slab bearing alayer of adhesive will only be bonded to the wall at a few points ofcontact. Furthermore, the surface of the walls of the ingot mould isoften not coherent, but consists of loosely adherent particles of ironoxide, or refractory residues from materials used as linings ofanti-piping compounds in previous ingot casting operations. Lining slabscannot be fixed to the walls using known adhesive systems without firstbrushing down the walls in order to remove the residues.

In addition to this small-scale unevenness, the walls of ingot mouldsare rarely flat; they usually have a camber, and the lining slab must bematched to this camber in use. Thus, a flat lining slab must be deformedto shape, and any adhesive attachment system must be able to withstandthe tendency of a resilient lining slab to return to a flatconfiguration.

Known adhesives suffer from several disadvantages: non-refractoryadhesives tend to perform their desired function inadequately whensubjected to the heat experienced both before and during pouring and inquantity are liable to combustion or even explosion; refractoryadhesives tend to leave an adherent residue on the ingot mould wallsafter the ingot has been stripped. If build-up of deleterious residueover successive operations is to be avoided the residue must be removed.

Thus the use of known adhesives has tended to create the need for moremeticulous cleaning of the moulds than the application of an air blastor wire brush as is normally practised. This extra cleaning is both timeconsuming and inconvenient.

The invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a schematic view and showing a method of hot topping an ingotmould in accordance with the present invention utilizing strips of asoft layer and FIG. 2 is a view similar to FIG. 1, except illustratingthe use of a continuous soft layer with an ingot mould having anirregular inner surface which has been exaggerated for sake of clarity.

According to a first feature of the present invention there is provideda method of hot topping an ingot mould by adhering preformed hot toplining slabs therein which comprises providing on at least one of thesurfaces which are to be adhered together a soft layer of diflicultlyflammable material, locating the lining slabs in the ingot mould andurging them against the wall thereof, thereby to deform the soft layer,the soft layer being adhered to the surface of the ingot mould by meansof an intermediate layer of adhesive. This intermediate thin layer isnot a fire risk and does act satisfactorily.

According to a particular feature of the present invention there isprovided a method of hot topping an ingot mould which comprisesattaching a hot top lining slab to the walls of the ingot mould via adeformable sealing material to which both the lining slab and the wallare adhered by an adhesive. This deformable sealing materialconstitutes, in such a case, the difficultly flammable soft layer justreferred to.

This method overcomes the'disadvantages associated with known adhesivesystems, and allows firm attachment of hot top lining slabs to ingotmould walls, despite the possible roughness of the walls and theircamber.

It is to be observed that this effect could not be obtained by merelyusing a thick layer of some organic adhesive, since such a thick layerwould constitute a considerable fire risk. By using a soft layer of lowflammability, coated with a thin layer of adhesive, good adhesion andgood mechanical matching may both be obtained at the same time.

Preferably the soft layer is located first on the hot top lining slabthough it may be adhered to the wall of the mould or head box and havethe slub adhered thereto afterwards. An ingot mould lined with hot toplining slabs as has been herein described is illustrated in the figures.In FIG. 1, an ingot mould 10 is lined with a hot top lining slab 12having a primer layer 14 thereon via strips of soft layer 16 andadhesive 18. In FIG. 2, an ingot mould 20 having an irregular innersurface (exaggerated for sake of illustration) is lined with a hot toplining slab 22 via a soft layer 24 with an adhesive layer 26 interposedbetween the soft layer 24 and the irregular inner surface of the ingotmould 20. The soft layer preferably has a thickness which is of theorder of the unevenness of the mould wall, e.g. 0.8 mm. to 1.5 mm. Thesoft layer may be formed in a wide variety of ways, and a wide varietyof materials may be used for its construction. The material may be softand resilient, for example polyurethane foam, unvulcanised neoprenesheet or sponge polypropylene or it may be non-resilient, for example, apasty or putty like composition, or a mastic. In some cases, e.g.certain putties or mastics, the material of the soft layer may itself besulficiently adhesive to hold itself on the slab prior to assembly ofthe slab on the wall, but in others, for example foam polyurethane, anintermediate adhesive layer may be employed. The soft layer may, in somecases, be made of material similar to that of which the hot top liningslab is made. The hot top lining slab is generally 0.5-5 cm. thick,though thinner facing slabs are also known and may also be applied bythe method of the invention.

In use, the presence of the soft layer allows the unevenness in theingot mould wall to be taken up, and also, in many cases, encapsulatesparticles of scale, dirt and the like and is adhered fast to the solidwall of the mould itself. The adherence between slab and mould wall iseffected by pressing the slab onto the mould wall. When that pressure isreleased, the movement of the slab away from the wall is taken up in thesoft material and the adhering surfaces are not pulled apart.

The soft layer need not extend over the whole of the surface of the slabor ingot mould wall, but may be present thereon as a number of discreteareas, e.g. in the form of strips or beads of soft layer.

In order to minimise absorption of adhesive, or the material of the softlayer itself, into the slab, it is often advantageous to prime or sizethe slab suitably.

A number of other considerations should be borne in mind in theselection of the material for the soft layer. Preferably, the soft layeris:

(a) capable of absorbing vibration or impact shock;

(b) readily capable of deformation when pressure is applied to the hottop lining slabs being positioned in the ingot mouldgreater contact areais achieved as the soft layer conforms to micro-irregularities andgeometric unevenness of the mould wall;

(c) able to maintain its functional soft condition in extremes ofhumidity and temperature which may be experienced in its storage;

((1) of sufficiently high tensile and shear strength to support theweight of the hot top lining slabs at ambient and elevated temperatures;

(e) possessed of sufficiently high internal shear strength at elevatedtemperatures, i.e. temperatures which it will experience during thecasting of steel so that the viscosity of the material does notdeteriorate to a sufficient extent to weaken the bond between ingotmould and lining slab by flowing;

(f) compatible with any adhesive used to adhere it to the slab or mouldwall; e.g. the material of the soft layer should not cause the adhesiveto form a readily detachable skin or film or absorb adhesive orotherwise adversely affect the adhesive properties thereof;

(g) capable of being sufficiently thermally degraded to make it possibleeasily to remove the residue from the mould after use. However, the rateof degradation should be such that adhesion between the lining and themould wall is not affected until a skull of solidified head metal hasformed within the hot top; it should not be ignited at any stage.

Materials which have been formed especially for use as the soft layerare, for example, extruded sheets or ribbons of compositions comprisingone or more powdered fillers such as powdered calcium carbonate orprecipitated chalk, or talc and binders such as plasticised syntheticresins, non-drying alkyd resins, blended vegetable oils or compoundedmixtures of any of these. Alternatively, the binder may be a dryingvegetable oil, such as a linseed oil (e.g. stand oils, blown oils orbodied blown oils) to which an antioxidant has been added. The viscosityrange of the oils used may be, for example, 40-3000 poises at 25 C. Theoils may also contain other additives such as viscosity stabilisers,oxidation and polymerisation catalysts, bodying agents (e.g. bentoneclays) and polyisobutylones (to increase elongation). These compositionsmay also contain a proportion of fibrous material such as fiberizednewsprint or kraft paper, asbestos, glass wool or slag wool to improvethe tensile and shear strength of the composition. Further the fillermay be precoated e.g. with a resin or a stearate to prevent excessabsorption of the resin binder.

Any adhesive used to secure the soft material either to the hot toplining slab or to the ingot mould wall should preferably;

(a) be a pressure-sensitive material which has a high degree of tack.

(b) remain tacky and not deteriorate under extremes of humidity andtemperature.

(c) provide a flexible/ resilient film when dry.

(d) operate at temperatures between 15 and +400 C.

(e) be compatible with the material of the soft layer and with theprimer or size if used.

(f) be degraded or carbonised during the casting operation so as not toleave any nndecomposed portion of the adhesive on the ingot mould wallto the possible detriment of subsequent lining or casting operations.

The primer and/or size (when used) is applied to the hot topping elementslab (which may be insulating or exothermic, flexible or rigid) toprevent excessive absorption of adhesive by the hot topping composition.The primer or size should be flexible or resilient when dry, preferablynon-inflammable and render the hot top lining element surfacesubstantially non-permeable. It preferably contains a filler or pigment(such as titania, China clay, gypsum or other commonly used paintfillers) which assists in leveling the surface of the hot top liningslab so as to present a smoother surface to which is applied theadhesive and then the layer of soft material. The primer base may be,for example, an aqueous emulsion of polyvinyl acetate or of Z-ethylhexyl acrylate. A dilute emulsion of the adhesive which will be used maybe employed if desired. A suitable commercially available size is DunlopChemical Products Divisions Politone.

In practice, the primer and soft layers are preferably applied to thesurface of the hot topping slabs which are to be stuck to the ingotmould wallthis may be in a series of strips or beads, or it may coverthe whole face of the element. A particularly preferred arrangement isthat of a number of spaced parallel strips each /22 wide, spaced /2-2apart. It is very preferable to apply the soft layer along at least thatedge of each slab which will be lowest in use.

In a very convenient manner of performing the invention, the softmaterial is employed as strips of an extruded composition having a layerof adhesive applied to both faces. The adhesive/soft material sandwichmay then be protected by the application of a leaf of conventionalrelease paper to each face. The adhesive/ soft material sandwich isapplied to the primed areas of the hot topping element after removal ofone of the release papers. The second release paper is removedimmediately prior to fixing the slab in the ingot mould. By applyingpressure to the hot top lining slab it is caused to adhere firmly to themould wall, and the soft material is deformed to accommodate all thesurface irregularities of the mould wall. The soft material may in somecases flow and tend to encapsulate any loose particles which may beadhering to the mould wall, and allow the adhesive to penetrate betweenthe particles themselves. The technique may be employed successfullywith ingot moulds at temperatures ranging from -15 to +400 C. Naturally,it is unnecessary to use release papers if the adhesive/soft materialsandwich is applied directly to the hot topping slab.

Hot topping slabs of particular suitability for use in the presentinvention are those described and claimed in our copending US.application Ser. No. 24,021, now abandoned, assigned to a commonassignee.

The following example will serve to illustrate the invention: For use asthe soft materials a mastic composition was prepared from the mixture oftwo parts by weight of precipitated chalk and one part by weight of anondrying alkyd resin. This composition was extruded into ribbons /2"wide and thick. Each face of the ribbon was coated with a 50% aqueousemulsion of poly 2 ethyl hexyl acrylate and allowed to dry. A suitablecoating Weight is 5-50 gms. of emuision per square foot, a coatingweight of -30 gms. per square foot being preferred. Each face was thenprotected with a strip of siliconetreated release paper. Insulating hottop slabs were then prepared to receive the adhesive sandwich bypainting the rear faces (i.e. those which were to be remote from thecast metal when functioning as hot topping insulators) with a primerconsisting of a partly hydrolised polyvinyl acetate emulsion containinga china clay filler. The release paper was removed from one face of astrip of the adhesive/mastic sandwich which was then applied along thebottom edge of the rear face of one of the insulating slabs. Furtherstrips were then applied to the slab, parallel to the first strip, andspaced at /2 intervals, over the complete face of the slab. Theremaining slabs were prepared for use in a similar Way. The slabs werethen easily fixed in position in the head of an ingot mould by merelyremoving the second release paper and pressing the slabs into theappropriate position.

It will be appreciated that, although reference has been made to as manyas three separate components (primer, adhesive and soft material), itmay sometimes be possible to incorporate two or all of these componentsinto one composite material. For example, it may be possible to use asoft material which is also sufiiciently adhesive to perform thefunction of adhering to the hot top-ping slab. It may also be possibleto incorporate an impermeable layer during the manufacture of the hottopping element and thereby obviate the need for a primer application.

It is to be understood that the present invention includes not only themethod set out above, but also the materials for carrying out such amethod. In particular, the invention includes the strips of softmaterial of the type noted coated each side with a pressure-sensitiveadhesive, and also includes ingot moulds or hot top slabs, sleeves orthe like having such strips adhered thereto.

We claim as our invention:

1. In the method of hot topping an ingot mould having a nonuniformsurface by adhering preformed hot top lining slabs to the head portionsurface of the mould, the improvement which comprises providing liningslabs having a soft layer of ditficultly flammable material covering atleast part of one surface of the lining slabs and adhered thereto withthe other surface of the soft layer being free, providing an adhesive onat least one of the head portion and free surfaces, said difficultlyflammable material being capable of being deformed to conform to thesurface of the head portion, locating the lining slabs adjacent the headportion of the mould with the soft layer next to the head portionsurface and urging the lining slabs against the head portion to deformthe soft layer to conform to the head portion surface and adhesivelybond the lining slab to the head portion surface.

2. A method according to claim 1 wherein both the hot top lining slabsand the head portion surface of the mould are adhered by an adhesive tothe soft layer.

3. A method according to claim 1 wherein the thickness of the soft layeris 0.8-1.5 mm.

4. A method according to claim 1 wherein the soft layer comprises anumber of discrete strips of material.

5. A method according to claim 1 wherein the face of each of the hot toplining slabs having the soft layer thereon has been primed.

6. A method according to claim 5 wherein the hot top lining slabs aretreated with an emulsion of a polymeric film-forming material containinga material selected from the group consisting of pigments and fillers.

7. A method according to claim 1 wherein the adhesive is a polymer of 2ethyl hexyl acrylate.

8. A method according to claim 1 wherein the soft layer comprises amixture of a powdered filler and a fluid binder selected from the groupconsisting of plasticised synthetic resins, non-drying alkyd resins andvegetable oils.

9. A method according to claim 8 wherein the filler is a member selectedfrom the group consisting of precipitated chalk, fibrous talc and talc.

16. A method according to claim 1 wherein the soft layer is apolyurethane foam.

11. A method according to claim 1 wherein the soft layer is anunvulcanized neoprene sheet.

12. A method according to claim 1 wherein the soft layer is a spongepolypropylene.

13. A method according to claim 1 wherein the soft layer is a putty.

14. A method according to claim 1 wherein the soft layer is a mastic.

15. In the method of hot topping an ingot mould having a nonuniformsurface by adhering preformed hot top lining slabs to the head portionsurface of the mould, the improvement which comprises providing a softlayer of difiicultly flammable material capable of being deformed toconform to the surface of the head portion, adhering the soft layer tothe head portion, providing lining slabs, adhering one surface of thelining slabs to the soft layer, the soft layer covering at least part ofthe adhered surface of the lining slabs, an adhesive being provided onat least one of the heat portion and the surface of the lining slabswhich is adhered to the soft layer and urging the lining slabs againstthe head portion to deform the soft layer to conform to the head portionsurface and adhesively bond the lining slab to the head portion surface.

References Cited UNITED STATES PATENTS 1,838,658 12/1931 Chapin 1062512,864,882 12/1958 Snell 260-33.6 AQ 3,320,108 5/1967 Lande 156-2193,484,073 12/ 1969 Pusch 249 -201 ROBERT D. BALDWIN, Primary ExaminerUS. Cl. X.R.

